Abstract:

A semiconductor device includes: an insulating film including a porous
insulating material and formed above a substrate; an interconnection wire
including copper and buried in a groove formed at least in an obverse
surface of the insulating film; and a barrier insulating film including
an insulating material containing a nitrogen heterocyclic compound and
formed over the insulating film and the interconnection wire.

Claims:

1. A semiconductor device comprising:an insulating film including a porous
insulating material and formed above a substrate;an interconnection wire
including copper and buried in a groove formed at least in an obverse
surface of the insulating film; anda barrier insulating film including an
insulating material containing a nitrogen heterocyclic compound and
formed over the insulating film and the interconnection wire.

2. The semiconductor device according to claim 1, wherein the barrier
insulating film is a coating-type insulating material.

3. The semiconductor device according to claim 1, wherein the nitrogen
heterocyclic compound is a compound selected from a group including a
compound having an imidazole skeleton, a compound having a pyrrole
skeleton, a compound having an indole skeleton, a compound having a
purine skeleton, a compound having a pyrazole skeleton, a compound having
an oxazole skeleton, and a compound having a thiazole skeleton.

4. The semiconductor device according to claim 1, wherein the barrier
insulating film is a continuous film.

5. A method of manufacturing a semiconductor device comprising:forming an
insulating film including a porous insulating material above a
substrate;forming an opening in the insulating film;forming an
interconnection wire including copper in the opening; andforming a
barrier insulating film including an insulating material containing a
nitrogen heterocyclic compound over the insulating film and the
interconnection wire.

6. A method of manufacturing a semiconductor device according to claim 5,
wherein the barrier insulating film is formed by performing coating with
an insulating film forming composition and then hardening the insulating
film forming composition.

7. A method of manufacturing a semiconductor device according to claim 5,
wherein the barrier insulating film is formed from the insulating
material containing the nitrogen heterocyclic compound which is a
compound selected from a group including a compound having an imidazole
skeleton, a compound having a pyrrole skeleton, a compound having an
indole skeleton, a compound having a purine skeleton, a compound having a
pyrazole skeleton, a compound having an oxazole skeleton, and a compound
having a thiazole skeleton.

8. A method of manufacturing a semiconductor device according to claim 5,
further comprising washing with an alcohol-type solvent or a ketone-type
solvent after the formation of the interconnection wire and before the
formation of the barrier insulating film.

9. A method of manufacturing a semiconductor device according to claim 8,
wherein the alcohol-type solvent is isopropyl alcohol, ethanol, or
methanol.

10. A method of manufacturing a semiconductor device according to claim 8,
wherein the ketone-type solvent is acetone, methyl ethyl ketone, or
methyl isobutyl ketone.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001]This application is based upon and claims the benefit of priority of
the prior Japanese Patent Application No. 2008-181182, filed on Jul. 11,
2008, the entire contents of which are incorporated herein by reference.

FIELD

[0002]The present invention relates to a semiconductor device and a method
of manufacturing the same. More particularly, the present invention
relates to a semiconductor device having a porous insulating film, and a
method of manufacturing the same.

BACKGROUND

[0003]With increasing integration and improving device density of
semiconductor integrated circuits, increasing demand exists for more
multilayered semiconductor devices. On the other hand, the spacing of
interconnect is becoming smaller with growing integration, resulting in
the problem of wiring delay due to an increased interconnects
capacitance.

[0004]A wiring delay T, which is subject to the effects of interconnect
resistance and interconnect capacitance, is expressed as: T∝CR,
where R represents the interconnect resistance and C represents the
interconnects capacitance. Based on this expression, the interconnects
capacitance C is expressed as C=ε0εrS/d, where
d represents an interconnect spacing, S represents an electrode area (the
area of side surfaces of opposed interconnection wires), εr
represents the dielectric constant of an insulating material provided
between adjacent interconnection wires, and ε0 represents
the dielectric constant of a vacuum. Therefore, lowering the dielectric
constant of an insulating film is effective in reducing the wiring delay.

[0005]Such insulating materials heretofore used include an inorganic film,
such as of silicon dioxide (SiO2), silicon nitride (SiN) or
phosphosilicate glass (PSG), and an organic polymer such as polyimide.
However, a CVD-SiO2 film formed by CVD, which is most frequently
used in semiconductor devices, has a dielectric constant of about 4. An
SiOF film, which is being studied as a low dielectric constant CVD film,
has a dielectric constant of about 3.3 to about 3.5, but exhibits high
moisture absorption. The dielectric constant of the SiOF film rises
undesirably with increasing absorption of moisture.

[0006]In recent years, attention has been focused on a porous insulating
film as an insulating material having an even lower relative
permittivity. Such a porous insulating film is an insulating film having
a plurality of pores therein.

SUMMARY

[0007]According to aspects of an embodiment, a semiconductor device
includes: an insulating film including a porous insulating material and
formed above a substrate; an interconnection wire including copper and
buried in a groove formed at least in an obverse surface of the
insulating film; and a barrier insulating film including an insulating
material containing a nitrogen heterocyclic compound and formed over the
insulating film and the interconnection wire.

[0008]The object and advantages of the invention will be realized and
attained by means of the elements and combinations particularly pointed
out in the claims.

[0009]It is to be understood that both the foregoing general description
and the following detailed description are exemplary and explanatory and
are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF DRAWINGS

[0010]FIG. 1 is a schematic sectional view illustrating a structure of a
semiconductor device according to one embodiment; and

[0011]FIGS. 2A to 2L are sectional views illustrating processes of a
method of manufacturing a semiconductor device according to one
embodiment.

DESCRIPTION OF EMBODIMENTS

[0012]A porous insulating material has a relative permittivity lowered by
the provision of pores therein. Such a porous insulating material having
pores therein, however, has a low strength and hence may be susceptible
to damage by plasma during film deposition when a CVD-type insulating
film is formed thereon. When damaged, the porous insulating film may have
deteriorated properties including an increased relative permittivity and
a lower insulating property.

[0013]The semiconductor device disclosed herein makes it possible to
reduce damage to an insulating film including the porous material during
formation of a barrier insulating film serving to prevent diffusion of
copper from interconnection wires. Thus, it is possible to prevent a rise
in the dielectric constant of the insulating film including the porous
material and deterioration in the insulating property of the insulating
film. Thus, a semiconductor device having a low interconnect capacitance
and a high insulating property may be realized.

[0014]A semiconductor device and a method of manufacturing the same
according to one embodiment will be described with reference to FIGS. 1
and 2A to 2L.

[0015]FIG. 1 is a schematic sectional view illustrating a structure of the
semiconductor device according to the present embodiment, and FIGS. 2A to
2L are sectional views illustrating processes of a method of
manufacturing the semiconductor device according to the present
embodiment.

[0016]Referring first to FIG. 1, description will be made of the structure
of the semiconductor device according to the present embodiment.

[0017]A device isolation insulating film 12 is buried in an obverse
surface of a semiconductor substrate 10. On an active region of the
semiconductor substrate 10 defined by the device isolation insulating
film 12, a MIS transistor 20 is formed which includes a gate electrode 16
formed on the semiconductor substrate 10 via an intervening gate
insulating film 14, and source/drain regions 18 formed in the
semiconductor substrate 10 on opposite sides of the gate electrode 16.

[0018]An interlayer insulating film 22 is formed over the semiconductor
substrate 10 and the MIS transistor 20. Contact plugs 24 each connected
to respective source/drain regions 18 are buried in the interlayer
insulating film 22.

[0019]An etching stopper film 26 and an interlayer insulating film 28
including a porous insulating material are formed over the interlayer
insulating film 22 in which the contact plugs 24 are buried.
Interconnection wires 40 connected to respective contact plugs 24 are
buried so as to extend through the interlayer insulating film 28 and the
etching stopper film 26.

[0020]On the interlayer insulating film 28 in which the interconnection
wires 40 are buried, there are formed a barrier insulating film 42
including an insulating material containing a nitrogen heterocyclic
compound, an interlayer insulating film 44 including the porous
insulating material, an etching stopper film 46, and an interlayer
insulating film 48 including the porous insulating material. A via plug
64a is buried so as to extend through the barrier insulating film 42,
interlayer insulating film 44, and etching stopper film 46. An
interconnection wire 64b formed integrally with the via plug 64a is
buried in the interlayer insulating film 48.

[0021]A barrier insulating film 66 including the insulating material
containing the nitrogen heterocyclic compound is formed over the
interlayer insulating film 48 in which the interconnection wire 64b is
buried. A multi-level interconnection layer 70 including an
interconnection wire 68 is formed over the barrier insulating film 66.

[0022]An etching stopper film 72 and an interlayer insulating film 74 are
formed over the multi-level interconnection layer 70. A contact plug 78
connected to the interconnection wire 68 is buried so as to extend
through the interlayer insulating film 74 and the etching stopper film
72.

[0023]A pad electrode 80 connected to the interconnection wire 68 via the
contact plug 78 is formed on the interlayer insulating film 74 in which
the contact plug 78 is buried. Over the interlayer insulating film 74
formed with the pad electrode 80, a passivation film 82 is formed which
has an opening 84 over the pad electrode 80.

[0024]In the semiconductor device thus structured according to the present
embodiment, the barrier insulating films 42 and 66 each include the
insulating material containing the nitrogen heterocyclic compound. The
provision of such a barrier insulating film is to prevent a diffusion of
copper (Cu), which is a major constituent of the interconnection wires 40
and 64, into the interlayer insulating film located adjacent thereto. In
the insulating material containing the nitrogen heterocyclic compound,
nitrogen, which has an unshared electron pair in the skeleton of the
nitrogen heterocyclic compound, captures Cu and hence contributes to the
prevention of Cu diffusion. Thus, the barrier insulating film functions
as a barrier against Cu diffusion.

[0025]Such nitrogen heterocyclic compounds include, without particular
limitation, nitrogen pentacyclic or hexacyclic compounds, or derivatives
thereof. Examples of such compounds include: compounds of the type having
an imidazole skeleton (e.g., polyimidazole polymers); compounds of the
type having a pyrrole skeleton (e.g., polypyrrole polymers); compounds of
the type having an indole skeleton (e.g., polyindole polymers); compounds
of the type having a purine skeleton (e.g., polypurine polymers);
compounds of the type having a pyrazole skeleton (e.g., polypyrazole
polymers); compounds of the type having an oxazole skeleton (e.g.,
polyoxazole polymers); and compounds of the type having a thiazole
skeleton (e.g., polythiazole polymers). These compounds are coating-type
insulating materials each of which may be formed into a film by a coating
process (e.g., SOD (Spin On Dielectric) process).

[0026]In general, a Cu diffusion preventing film includes a film grown by
plasma CVD such as, for example, an SiOC film. In forming a barrier
insulating film by plasma CVD, however, the interlayer insulating film
which underlies the barrier insulating film is exposed to plasma during
the barrier insulating film forming process. The porous insulating
material, which has a relative permittivity lowered by the provision of
pores therein, has a low bulk strength and is weak against plasma.
Thereforewhen each of the interlayer insulating films 28 and 48 is formed
using the porous insulating material as in the present embodiment, porous
insulating material properties may be deteriorated by plasma generated
during deposition of the barrier insulating film. For example, the porous
insulating material may have an increased relative permittivity or a
lower insulating property.

[0027]By using coating-type insulating films, the barrier insulating films
42 and 66 may be formed without damaging the porous insulating material
interlayer insulating films 28 and 48. Each of the barrier insulating
film materials mentioned above has a relative permittivity ranging from
2.7 to 3.6 for example, which is substantially equal to or less than the
relative permittivity (about 3.6) of the SiOC film usually used as a
barrier insulating film. Therefore, use of any one of the aforementioned
barrier insulating film materials makes it possible to lower the
dielectric constants of the interlayer insulating films.

[0028]Description will be made of the method of manufacturing the
semiconductor device according to the present embodiment with reference
to FIGS. 2A to 2L.

[0029]Initially, the device isolation insulating film 12 is formed in the
semiconductor substrate 10 (e.g., a silicon substrate) by a process such
as Shallow Trench Isolation (STI).

[0030]The MIS transistor 20, which includes the gate electrode 16 formed
on the semiconductor substrate 10 via the intervening gate insulating
film 14 and the source/drain regions 18 formed in the semiconductor
substrate 10 on opposite sides of the gate electrode 16, is formed on an
active region of the semiconductor substrate 10 defined by the device
isolation insulating film 12 in a similar manner as a typical MIS
transistor manufacturing method (see FIG. 2A).

[0031]A phosphosilicate glass (PSG) film having a thickness of 1.5 μm
for example is deposited, by CVD for example, on the semiconductor
substrate 10 formed with the MIS transistor 20.

[0032]The surface of the PSG film is planarized by polishing, for example
Chemical Mechanical Polishing (CMP), to form the interlayer insulating
film 22 having a planarized surface.

[0033]Contact holes reaching the respective source/drain regions 18
through the interlayer insulating film 22 are formed by photolithography
and dry etching.

[0034]A barrier metal film, such as a titanium nitride (TiN) film having a
thickness of 10 nm for example, and a tungsten (W) film having a
thickness of 500 nm for example, are deposited as contact plug materials
over the entire surface by, for example, sputtering.

[0035]The tungsten film and titanium nitride film on the interlayer
insulating film 22 are selectively removed by, for example, CMP to form
the contact plugs 24 each buried in respective contact holes and
connected to respective source/drain regions 18 (see FIG. 2B).

[0036]Silicon oxycarbide (SiOC) is deposited by, for example, CVD to a
film thickness of 30 nm, for example, over the interlayer insulating film
22 in which the contact plugs 24 are buried, to form the SiOC etching
stopper film 26.

[0037]The interlayer insulating film 28 including the porous insulating
material is formed to a thickness of 150 nm, for example, over the
etching stopper film 26 by, for example, a coating process (e.g., SOD
(Spin On Dielectric) process) (see FIG. 2c).

[0038]Examples of usable coating-type porous insulating materials include,
without particular limitation, porous HSQ (hydrogensilsesquioxane) which
is an inorganic SOG (silicon on glass) material, and porous MSG
(methylsilsesquioxane) which is an organic SOG material.

[0039]Such porous insulating materials are classified into, for example,
two types: a template type, which is prepared by a process including
adding a heat decomposable resin or the like to the organic SOG material
and allowing the heat decomposable resin to thermally decompose by
heating to form pores, and a non-template type which is prepared by a
process including forming silica particles in alkali and utilizing
interparticle spaces to form pores. Of the two types, the non-template
type is preferable because minute pores may be formed uniformly. Specific
non-template type porous MSGs include NCS series products of JGC
Catalysts and Chemicals Ltd., and LKD series products of JSR Corporation.

[0040]An insulating film including a coating-type insulating material may
be formed, for example, by performing spin coating with an insulating
film forming composition and curing the insulating film forming
composition at a temperature of about 350° C. to about 450°
C. An insulating film including porous MSQ may be formed, for example, by
performing coating with the insulating film forming composition and then
curing the insulating film forming composition at about 400° C.
for about 60 minutes. The interlayer insulating film 28 including porous
MSQ thus formed has a relative permittivity of about 2.4 for example.

[0041]A photoresist film 30, having openings 32 in regions for forming
interconnection wire grooves for burying therein the interconnection
wires to be connected to the respective contact plugs 24, is formed over
the interlayer insulating film 28 by photolithography.

[0042]The interlayer insulating film 28 and the etching stopper film 26
are subjected to dry etching using the photoresist film 30 as a mask, to
form interconnection wire grooves 34 each reaching one of the contact
plugs 24 through the interlayer insulating film 28 and the etching
stopper film 26 (see FIG. 2D).

[0043]The photoresist film 30 is removed by ashing, for example.

[0044]A tantalum (Ta) film having a thickness of 15 nm, for example, is
formed over the entire surface by sputtering, for example, to form a
barrier metal film 36 including the Ta film.

[0045]Copper (Cu) is deposited to a film thickness of 50 nm, for example,
over the barrier metal film 36 by sputtering, for example, to form a Cu
seed film (not depicted).

[0046]A Cu film is grown by, for example, electroplating using the seed
film as a seed, to form a Cu film 38 having a total thickness of, for
example, 300 nm inclusive of the thickness of the seed layer.

[0047]The Cu film 38 and barrier metal film 36 on the insulating film 28
are selectively removed by CMP, for example, to form the interconnection
wires 40 buried in the respective interconnection wire grooves 34 (see
FIG. 2E).

[0048]The surface of the interlayer insulating film 28 in which the
interconnection wires 40 are buried is washed with an alcohol-type
solvent or a ketone-type solvent. An alcohol-type solvent is desirably a
substance which can stably maintain a liquid state at room temperature,
but is not particularly limited thereto. Examples of usable alcohol-type
solvents include isopropyl alcohol, ethanol, and methanol. A ketone-type
solvent is desirably a substance which can stably maintain a liquid state
at room temperature, but is not particularly limited thereto. Examples of
usable ketone-type solvents include acetone, methyl ethyl ketone, and
methyl isobutyl ketone.

[0049]The barrier insulating film 42 including the insulating material
containing the nitrogen heterocyclic compound is formed by the SOD
process over the interlayer insulating film 28 in which the
interconnection wires 40 are buried (see FIG. 2F).

[0050]The above-described washing process using the alcohol-type solvent
or ketone-type solvent serves as a pretreatment conducted prior to the
deposition of the barrier insulating film 42. In cases where a film
forming process other than the SOD process, such as plasma CVD, is used
for the formation of a barrier insulating film, pretreatment in film
deposition is possible by conducting a plasma treatment or the like prior
to the film deposition. In the present embodiment on the other hand, the
surface over which the barrier insulating film 42 is to be formed is
cleaned by washing using the alcohol-type solvent or ketone-type solvent
to allow the barrier insulating film 42 to be formed by the SOD process.

[0051]The SOD process is used for the formation of the barrier insulating
film 42 so that the barrier insulating film 42 may be formed without
damaging the porous insulating material interlayer insulating film 28.

[0052]The barrier insulating film 42, which is a film for preventing
diffusion of Cu from the interconnection wires 40, is usually an
insulating film having a high density. A film grown by plasma CVD, for
example, an SiOC film is typically used for such an insulating film. In
forming such a barrier insulating film by plasma CVD, however, the
interlayer insulating film which underlies the barrier insulating film is
exposed to plasma during the barrier insulating film forming process.

[0053]The porous insulating material, which has a relative permittivity
lowered by the provision of pores therein, has a low bulk strength due to
the provision of pores and is weak against plasma. Therefore, when the
interlayer insulating film 28 is formed using the porous insulating
material as in the present embodiment, the porous insulating material
might have properties deteriorated by plasma generated during deposition
of the barrier insulating film. For example, the porous insulating
material might have an increased relative permittivity or a lower
insulating property.

[0054]The present embodiment uses the SOD process for the formation of the
barrier insulating film 42 because the SOD process does not damage the
underlying material during the film forming process.

[0055]Nitrogen heterocyclic compounds may include, without particular
limitation, compounds of the type having an imidazole skeleton (e.g.,
polyimidazole polymers), compounds of the type having a pyrrole skeleton
(e.g., polypyrrole polymers), compounds of the type having an indole
skeleton (e.g., polyindole polymers), compounds of the type having a
purine skeleton (e.g., polypurine polymers), compounds of the type having
a pyrazole skeleton (e.g., polypyrazole polymers), compounds of the type
having an oxazole skeleton (e.g., polyoxazole polymers), and compounds of
the type having a thiazole skeleton (e.g., polythiazole polymers). The
barrier insulating film is formed using the insulating material
containing the nitrogen heterocyclic compound because the presence of
nitrogen having an unshared electron pair in the skeleton of the nitrogen
heterocyclic compound contributes to the prevention of Cu diffusion.

[0056]The following is an example of a method of forming the barrier
insulating film 42 including a polyimidazole polymer.

[0057]Initially, a barrier insulating film forming composition is prepared
which includes 1,3,5-tricarboxyladamantane as a first monomer,
N,N,N-triisopropylidenebiphenyl-1,3,4,3'-tetraamine as a second monomer,
and a solvent.

[0058]Examples of usable first monomers include, without particular
limitation, adamantane derivatives of the type having at least one
carboxyl group. Examples of such adamantane derivatives include
1-carboxyladamantane derivatives, 1,3-dicarboxyladamantane derivatives,
1,3,5-tricarboxyladamantane derivatives, and
1,3,5,7-tetracarboxyladamantane derivatives. These adamantane derivatives
may be used as mixtures. Examples of usable second monomers include,
without particular limitation, diamine derivatives of the type having at
least two amino groups, triamine derivatives, and tetraamine derivatives.

[0059]The barrier insulating film forming composition thus prepared is
applied onto the interlayer insulating film 28 in which the
interconnection wires are buried with use of a spin-coater.

[0060]The barrier insulating film forming composition is polymerized and
cured by a heat treatment at a temperature ranging from 350° C. to
450° C. (for example, 400° C.) for an hour using a hot
plate. In this way, the barrier insulating film 42 including the
polyimidazole polymer is formed which has a thickness of about 20 to
about 50 nm (for example, 30 nm).

[0061]In forming the barrier insulating film 42, irradiation with
ultraviolet rays may be conducted in addition to the heat treatment.
Irradiation with ultraviolet rays contributes to acceleration of the
polymerization reaction of the barrier insulating film forming
composition. Applicable ultraviolet rays include short-wavelength
ultraviolet rays and broadband ultraviolet rays having multiple
wavelengths from 150 to 500 nm. For example, an ultraviolet ray having
wavelengths of 185 nm and 254 nm and an electron energy ranging from 4.9
to 6.7 eV may be used.

[0062]The barrier insulating film forming composition used in the present
embodiment does not contain sacrificial organic molecules as contained in
the template-type porous insulating material. A material containing
sacrificial organic molecules allows pores to be formed in the resulting
film when the sacrificial organic molecules come out of the film. The
barrier insulating film forming composition used in the present
embodiment, on the other hand, does not contain sacrificial organic
molecules and hence does not allow pores to be formed in the resulting
barrier insulating film 42. In the present description, a film having no
pores formed therein is referred to as a "continuous film".

[0063]The barrier insulating film 42 of the polyimidazole polymer thus
formed has a relative permittivity of about 2.9, which is lower than 3.6,
which is the relative permittivity of a typical SiOC film.

[0064]The interlayer insulating film 44 including the porous insulating
material is formed by the SOD process, for example, to a thickness of 150
nm, for example, over the barrier insulating film 42. The interlayer
insulating film 44 may be formed using the same method and material as
used for the formation of the above-described interlayer insulating film
28.

[0065]An SiOC film having a thickness of 30 nm, for example, is deposited
over the interlayer insulating film 44 by plasma CVD, for example, to
form the etching stopper film 46 including the SiOC film.

[0066]The interlayer insulating film 48 including the porous insulating
material is formed to a thickness of 150 nm, for example, over the
etching stopper film 46 by the SOD process, for example, (see FIG. 2G).
The interlayer insulating film 48 may be formed using the same method and
material as used for the formation of the above-described interlayer
insulating film 28.

[0067]A photoresist film 50 having an opening 52 in a region to form a via
hole to be connected to the interconnection wire 40 is formed over the
interlayer insulating film 48 by photolithography.

[0068]The interlayer insulating film 48, etching stopper film 46, and
interlayer insulating film 44 are sequentially subjected to dry etching
using the photoresist film 50 as a mask to form a via hole 54 reaching
the barrier insulating film 42 (see FIG. 2H).

[0069]The presence of nitrogen in the barrier insulating film 42 including
the polyimidazole polymer allows for etching selectivity between the
interlayer insulating film 44 including the porous insulating material
and the barrier insulating film 42. In etching the interlayer insulating
film 48, the etching stopper film 46, and the interlayer insulating film
44, use of C4F6 gas, for example, may ensure a selection ratio
of about 10 for the barrier insulating film 42.

[0070]The photoresist film 50 may be removed by, for example, ashing.

[0071]A photoresist film 56 having an opening 58 in a region to form an
interconnection wire groove for burying therein an interconnection wire
to be connected to the via hole 54, is formed over the interlayer
insulating film 48 by photolithography.

[0072]The interlayer insulating film 48 is subjected to dry etching using
the photoresist film 56 as a mask and the etching stopper film 46 as a
stopper, to form an interconnection wire groove 60 reaching the etching
stopper film 46 through the interlayer insulating film 48.

[0073]The barrier insulating film 42 is subjected to dry etching using the
photoresist film 56 and the etching stopper film 46 as masks to extend
the via hole 54 down to the interconnection wire 40 (see FIG. 2I). The
barrier insulating film 42 may be selectively etched relative to the
interlayer insulating films 44 and 48 and etching stopper film 46 by
using, for example, a fluorine compound containing nitrogen.

[0074]The photoresist film 56 is removed by ashing, for example.

[0075]Ta is deposited to a film thickness of 15 nm, for example, over the
entire surface by sputtering, for example, to form a Ta barrier metal
film 61.

[0076]Copper (Cu) is deposited to a film thickness of 50 nm, for example,
over the barrier metal film 61 by sputtering, for example, to deposit a
Cu seed film (not depicted).

[0077]A Cu film is grown by, for example, electroplating using the seed
film as a seed to form a Cu film 62 having a total thickness of, for
example, 300 nm inclusive of the thickness of the seed layer.

[0078]The Cu film 62 and barrier metal film 61 on the interlayer
insulating film 48 are selectively removed by CMP, for example, to
integrally form the via plug 64a buried in the via hole 54 and the
interconnection wire 64b buried in the interconnection wire groove 60
(see FIG. 2J). A fabrication process for integrally forming the via plug
64a and the interconnection wire 64b is called a "dual damascene
process".

[0079]The surface of the interlayer insulating film 48 in which the
interconnection wire 64b is buried is washed with an alcohol-type solvent
or a ketone-type solvent. This process is the same as the pretreatment
process performed prior to the formation of the above-described barrier
insulating film 42.

[0080]The barrier insulating film 66 including the insulating material
containing the nitrogen heterocyclic compound is formed over the
interlayer insulating film 48 in which the interconnection wire 64b is
buried in the same manner as the method of forming the barrier insulating
film 42, for example (see FIG. 2K).

[0081]Thereafter, the multi-level interconnection layer 70 including an
interconnection wire is formed by an interconnection wire forming process
similar to the above-described process.

[0082]The SiOC etching stopper film 72, for example, and the silicon oxide
film interlayer insulating film 74 are formed over the multi-level
interconnection layer 70 by, for example, CVD.

[0083]A contact hole 76 reaching the interconnection wire 68 through the
interlayer insulating film 74 and the etching stopper film 72 is formed
by photolithography and dry etching.

[0084]The contact plug 78 connected to the interconnection wire 68 is
formed in the contact hole 76 in the same manner as the method of forming
the contact plug 24 for example.

[0085]An aluminum (Al) film is formed by sputtering, for example, over the
interlayer insulating film in which the contact plug is buried.

[0086]The aluminum film is patterned by photolithography and dry etching
to form the pad electrode 80 connected to the interconnection wire 68 via
the contact plug 78.

[0087]Silicon nitride is deposited by CVD, for example, over the
interlayer insulating film 74 formed with the pad electrode 80, to form
the silicon nitride passivation film 82.

[0088]The opening 84 exposing an electrode pad is formed in the
passivation film 82 by photolithography and dry etching.

[0089]In this way, the semiconductor device depicted in FIG. 1 according
to the present embodiment is manufactured.

[0090]The present embodiment described above may reduce damage to an
insulating film including the porous material during formation of a
barrier insulating film for preventing diffusion of copper from
interconnection wires. Thus, it is possible to reduce if not prevent a
rise in the dielectric constant of the insulating film including the
porous material and deterioration in the insulating property of the
insulating film, thereby to realize a semiconductor device having a low
interconnect capacitance and a high insulating property.

Variation Embodiments

[0091]The present embodiment is not limited to the foregoing embodiment,
but variations are possible.

[0092]For example, while the foregoing embodiment conducts the washing
treatment using the alcohol-type solvent or the ketone-type solvent as
the pretreatment prior to the formation of each of the barrier insulating
films 42 and 66 including the insulating material containing the nitrogen
heterocyclic compound, the present embodiment does not necessarily
require the washing treatment.

[0093]While the foregoing embodiment uses the SiOC film formed by plasma
CVD as an intermediate stopper layer (i.e., etching stopper film 46) to
be used in the dual damascene process, an insulating material containing
the nitrogen heterocyclic compound like the insulating material used to
form the barrier insulating films 42 and 66 may be used to form the
intermediate stopper layer. By so doing, it is possible to reduce damage
to the interlayer insulating film 44 which occurs during the formation of
the etching stopper film 46.

[0094]The present embodiment is not limited to the structure of the
semiconductor device or the method of manufacturing the same disclosed in
the foregoing embodiment. The present embodiment is widely applicable to
the production of semiconductor devices of the type having a copper
interconnection wire buried in a porous insulating film formed over an
underlying substrate. The film thickness and the material of each of the
layers forming the semiconductor device may be varied appropriately.

[0095]It is to be noted that the "underlying substrate", as used herein,
is meant to include not only a semiconductor substrate as made, such as a
silicon substrate, but also a semiconductor device formed with a device,
such as a transistor, and an interconnection layer.

Embodiment 1

[0096]A semiconductor device was manufactured according to the
manufacturing process described in the foregoing embodiment using a
polyimidazole polymer for the barrier insulating films 42 and 66 and
"NCS" (relative permittivity: 2.4) produced by JGC Catalysts and
Chemicals Ltd. for the interlayer insulating films 28 and 44.

[0097]The semiconductor device thus produced was measured for leakage
current by application of a voltage of 2 V to interconnection wires of a
comb-toothed shape (total length of opposed interconnection wires:
200,000 μm) having a line-and-space (L/S) of 70/70 nm and a thickness
of 130 nm. The leakage current thus measured was not more than
1×10-14 A, which proved that the semiconductor device had a
favorable leakage current characteristic. The semiconductor device had an
interconnect capacitance of 0.10 pF.

COMPARATIVE EXAMPLE 1

[0098]A semiconductor device was produced in the same manner as in Example
1 except that an SiOC film deposited by CVD using tetramethylsilane and
carbon dioxide gas was used for each of the barrier insulating films 42
and 66.

[0099]The semiconductor device thus produced was measured for leakage
current by application of a voltage of 2 V to interconnection wires of a
comb-toothed shape (total length of opposed interconnection wires:
200,000 μm) having a line-and-space (L/S) of 70/70 nm and a thickness
of 130 nm. The leakage current thus measured was about 1×10-7
A, which proved that interconnect leakage occurred. The semiconductor
device had an interconnect capacitance of 0.13 pF.

Embodiment 2

[0100]A semiconductor device was produced according to the manufacturing
process described in the foregoing embodiment using a polyimidazole
polymer for the barrier insulating films 42 and 66 and "Aurora ULK"
(relative permittivity: 2.6) produced by ASM Japan K.K. for the
interlayer insulating films 28 and 44.

[0101]The semiconductor device thus produced was measured for leakage
current by application of a voltage of 2 V to interconnection wires of a
comb-toothed shape (total length of opposed interconnection wires:
200,000 μm) having a line-and-space (L/S) of 70/70 nm and a thickness
of 130 nm. The leakage current thus measured was not more than
1×10-14 A, which proved that the semiconductor device had a
favorable leakage current characteristic. The semiconductor device had an
interconnect capacitance of 0.12 pF.

COMPARATIVE EXAMPLE 2

[0102]A semiconductor device was produced in the same manner as in Example
1 except that an SiOC film deposited by CVD using tetramethylsilane and
carbon dioxide gas was used for each of the barrier insulating films 42
and 66.

[0103]The semiconductor device thus produced was measured for leakage
current by application of a voltage of 2 V to interconnection wires of a
comb-toothed shape (total length of opposed interconnection wires:
200,000 μm) having a line-and-space (L/S) of 70/70 nm and a thickness
of 130 nm. The leakage current thus measured was about 1×10-7
A, which proved that interconnect leakage occurred. The semiconductor
device had an interconnect capacitance of 0.14 pF.

Embodiment 3

[0104]Using the manufacturing process described in the foregoing
embodiment, a semiconductor device produced without conducting a washing
treatment using an alcohol-type solvent or a ketone-type solvent prior to
the formation of each of the barrier insulating films 42 and 66 and a
semiconductor device manufactured by conducting the washing treatment
using the alcohol-type solvent or the ketone-type solvent prior to the
formation of each of the barrier insulating films 42 and 66, were
provided.

[0105]These semiconductor devices were each measured for the I-V
characteristic of a comb-toothed pattern having a W/S of 90/90 nm at
randomly selected points in the plane of a wafer having a diameter of 300
mm. As a result, both of the semiconductor devices exhibited favorable
I-V characteristics. As a result, the semiconductor device manufactured
by conducting the washing treatment using the alcohol-type solvent and
the semiconductor device manufactured using the ketone-type solvent both
exhibited reduced variations in I-V characteristics.

[0106]All examples and conditional language recited herein are intended
for pedagogical purposes to aid the reader in understanding the
principles of the invention and the concepts contributed by the inventor
to furthering the art, and are to be construed as being without
limitation to such specifically recited examples and conditions, nor does
the organization of such examples in the specification relate to a
showing of the superiority and inferiority of the invention. Although the
embodiments of the present inventions have been described in detail, it
should be understood that the various changes, substitutions, and
alterations could be made hereto without departing from the spirit and
scope of the invention.